@marcslp
Good luck with your project. I wanted to show what my enclosure looks like. I have had great experience with these BUD Industries enclosures as they are inexpensive, roomy and weatherproof. You had asked about buttons to reset the device, I like big push button switches which can me mounted on the board like this or panel mounted (use an IP-67 rated switch like this one).
On the watchdog timer, I have had good luck using a simple external one from TI, the TPL5010 which can be set to trigger anywhere from 100mSec to 2 hours by simply changing a resistor. I think this approach may be the cleanest. One item I forgot to mention to you in my last post. The Electron has the ability to report on what caused it to reset when it restarts. In my program, I use this feature to monitor and report (using a cloud.variable) on the number of reboots. This could be helpful as you deploy your devices to see if you still have software reliability problems which are being masked by the automatic resets.
Good luck and I hope this helps.
Chip